As new or improved magnetic applications or devices are developed, there is an increasing need for insulating magnetic materials which are chemically stable up to critical or Curie temperatures (T.sub.c) in excess of 125.degree. C. Such magnetic materials may be substituted for ferrites and other insulating magnetic compounds in applications such as radio frequency transformers, bulk magnets, magnetic and magneto-optic recording materials, for example. Such magnetic materials may also be included in photomagnetic switches, integrated optical devices, colloidal dispersions ("ferrofluids" and magnetic inks), thin film and multilayer magnets, magnetostrictive sensors, microwave materials, magnetic bubbles and soft magnetic materials with low coercive fields for AC motors, generators and transformers, as well as for magnetic imaging and transducers for medical implants, if the magnetic material is biocompatible.
Several low temperature organic and inorganic ferromagnetic compounds have been disclosed in the prior art. The reported organic ferro- and ferri- magnets are generally poorly characterized and yields are limited and not reproducible. J. Manriquez et al. "A Room-Temperature Molecular/Organic-Based Magnet", 252 Science 1415 (1991) discloses a molecular organic ferromagnetic compound having an empirical composition of V(TCNE.sub.x).multidot.y(CH.sub.2 Cl.sub.2), where TCNE is tetracyanoethylene, x is about 2 and y is about 1/2. The compound undergoes thermal decomposition at 350.degree. K. (77.degree. C.).
Z. Min-Guang, "An Ambient Temperature-Stable Organometallic Ferromagnet", 3 J. Phys. Condens. Matter 6695-6702 (1991) discloses an organometallic ferromagnet having a nominal composition of Cd.sub.2 Fe.sub.2 C.sub.36 H.sub.38 N.sub.4 O.sub.4. A magnetic hysteresis loop for the compound was observed with finite residual magnetization and coercivity at room temperature. However, the Mossbauer probe .sup.57 Fe in the compound does not sense any magnetic field and so the authors attributed the observed ferromagnetism to the organic free radicals.
A. Harutyunyan et al., "Organic Ferromagnets on Base of Metal-Phthalocyanines Doped by Alcali Metals," XIV(4) Materials Science 121-26 (1988) discloses a ferromagnetic compound formed by doping metal-phthalocyanines with alkali metals. The Curie temperature (T.sub.c) for [2Na-FePc] was found to be 590.degree. K. from the plot of saturation magnetization versus temperature. The (T.sub.c) for the cobalt compound was much higher and was not determined. However, the disclosed compounds are only stable in air up to 350.degree. K. (77.degree. C.).
There is also disclosed in the art an unstable manganese tetraphenylporphyrin (TPP)/tetracyanoethylene (TCNE) salt polymer which burst into flames on contact with air.
None of the prior art magnetic materials discussed above is stable at temperatures on the order of about 473.degree. K. (200.degree. C.) in an atmospheric environment and to much higher temperatures in vacuum or an inert atmosphere. There is a long-felt and unfulfilled need in the art for an insulating organic ferromagnetic material capable of remaining stable at temperatures in excess of 125.degree. C.